Windows 8 Pro Upgrade on build without OS

Dutcherling

Reputable
Feb 27, 2014
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4,510
I just build my first pc and installed Windows 8 on it. My product key seemed to work at first, as the OS was installed after I entered it, but now Windows claims I have not yet entered a product key and when I do so again (with the same key as before) it claims it is not valid.
Now I think my problem is that I bought Windows 8 Pro Upgrade without having a pre-existing Windows OS to upgrade from. Is it true (or likely) that that is indeed the problem? And if so, would uninstalling Windows 8, installing (a likely never to be activated version of) Windows 7, and then upgrading from that to Windows 8 again be a valid solution?
I found this as an answer to a similar problem of mine on a different forum, but it seems to silly to actually work.